Make buffer search aware of search direction (#24974)

This solves a couple of issues with Vim search by making the search
buffer and `SearchableItem` aware of the direction of the search. If
`SearchOptions::BACKWARDS` is set, all operations will be reversed. By
making `SearchableItem` aware of the direction, the correct active match
can be selected when searching backward.

Fixes #22506. This PR does not fix the last problem in that issue, but
that one is also tracked in #8049.

Release Notes:

- Fixes incorrect behavior of backward search in Vim mode

crates/workspace/src/searchable.rs

@@ -150,6 +150,7 @@ pub trait SearchableItem: Item + EventEmitter<SearchEvent> {
     ) -> Task<Vec<Self::Match>>;
     fn active_match_index(
         &mut self,
+        direction: Direction,
         matches: &[Self::Match],
         window: &mut Window,
         cx: &mut Context<Self>,
@@ -208,6 +209,7 @@ pub trait SearchableItemHandle: ItemHandle {
     ) -> Task<AnyVec<dyn Send>>;
     fn active_match_index(
         &self,
+        direction: Direction,
         matches: &AnyVec<dyn Send>,
         window: &mut Window,
         cx: &mut App,
@@ -315,13 +317,14 @@ impl<T: SearchableItem> SearchableItemHandle for Entity<T> {
     }
     fn active_match_index(
         &self,
+        direction: Direction,
         matches: &AnyVec<dyn Send>,
         window: &mut Window,
         cx: &mut App,
     ) -> Option<usize> {
         let matches = matches.downcast_ref()?;
         self.update(cx, |this, cx| {
-            this.active_match_index(matches.as_slice(), window, cx)
+            this.active_match_index(direction, matches.as_slice(), window, cx)
         })
     }